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Biomedical subjects

R S McLachlan

Publications and source records attributed to R S McLachlan.

At least 19 recordsLinked to original sources
PubMed2001

An autosomal dominant disorder with episodic ataxia, vertigo, and tinnitus.

The authors report an autosomal dominant episodic ataxia that is clinically distinct from the other episodic ataxias. Vestibular ataxia, vertigo, tinnitus, and interictal myokymia are prominent; attacks are diminished by acetazolamide. Linkage analyses of markers flanking the EA1 and EA2 loci demonstrate genetic exclusion from the other autosomal dominant episodic ataxias. The authors suggest EA3 for periodic vestibulocerebellar ataxia and EA4 for the disorder described here.

Adolescent↗
PubMed2000

Behaviors induced or disrupted by complex partial seizures.

We reviewed the neural mechanisms underlying some postictal behaviors that are induced or disrupted by temporal lobe seizures in humans and animals. It is proposed that the psychomotor behaviors and automatisms induced by temporal lobe seizures are mediated by the nucleus accumbens. A non-convulsive hippocampal afterdischarge in rats induced an increase in locomotor activity, which was suppressed by the injection of dopamine D(2) receptor antagonist in the nucleus accumbens, and blocked by inactivation of the medial septum. In contrast, a convulsive hippocampal or amygdala seizure induced behavioral hypoactivity, perhaps by the spread of the seizure into the frontal cortex and opiate-mediated postictal depression. Mechanisms underlying postictal psychosis, memory disruption and other long-term behavioral alterations after temporal lobe seizures, are discussed. In conclusion, many of the changes of postictal behaviors observed after temporal lobe seizures in humans may be found in animals, and the basis of the behavioral change may be explained as a change in neural processing in the temporal lobe and the connecting subcortical structures.

Animals↗
PubMed2000

Invasive electrographic recording techniques in temporal lobe epilepsy.

The management of uncontrolled partial epilepsy is a process dependent on a multidisciplinary and analytic approach. It is necessary to understand which lesions are epileptogenic, and if they are indeed responsible for the generation of seizures. In addition to localizing seizure onset, the functional and eloquent areas of the brain need to be identified. As in many other centres, we perform resective surgeries on the basis of combined information derived from seizure semiology, EEG abnormalities, neuroimaging and other tests of cerebral function. If surface EEG recording yields inconclusive or ambiguous results, then invasive intracranial techniques using intracerebral depth or subdural electrodes can be used to improve diagnostic or prognostic accuracy. The indications, principles, results and complications of these recording techniques based on extensive experience at two epilepsy surgery centres are reviewed.

Brain↗
PubMed2000

Management of antiepileptic drugs following epilepsy surgery: a review.

The favourable impact of surgery for intractable epilepsy on seizures is well documented. However, few studies have determined what changes in antiepileptic drug (AED) therapy occur following surgery. Alterations in AED blood levels in the immediate postoperative period can result in breakthrough seizures. In long term follow-up, one-third to one-half of seizure-free patients after temporal lobectomy, the most common type of epilepsy surgery, still require AED treatment which usually has been reduced from polytherapy to monotherapy. In our study of 93 patients followed two years after temporal lobectomy, polytherapy decreased from 78% before surgery to 14% postoperatively, while medication was discontinued in 44%. Early reduction from polytherapy to monotherapy can often be carried out in the immediate postoperative period but the most appropriate timing of cessation of AED treatment has yet to be determined. Patients undergoing extratemporal resections and other forms of epilepsy surgery associated with less favourable postoperative seizure control may achieve comparatively less reduction in antiepileptic medication. We generally do not recommend stopping AEDs prior to one year after surgery.

Anticonvulsants↗
PubMed2000

Evidence favoring genetic heterogeneity for febrile convulsions.

PURPOSE: Two large Canadian kindreds appearing to segregate febrile convulsions as an autosomal dominant trait were evaluated for linkage to three known FC loci, as well as other epilepsy loci. METHODS: Members of the two families were genotyped with microsatellite markers linked to the previously identified febrile convulsion loci, FEB1, FEB2, and GEFS+, and we performed two-point linkage analyses by assuming an autosomal dominant mode of inheritance. RESULTS: We report the exclusion of the FC trait in our families to FEB1 on 8q13-21 and to a second febrile convulsion locus on 19p13. Furthermore, we also excluded the GEFS+ locus on 19q13.1 as the cause of febrile convulsions in both kindreds. Microsatellite markers linked to juvenile myoclonic epilepsy (EJM1), benign neonatal familial convulsions EBN1 and EBN2, autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), idiopathic generalized epilepsy (EGI), progressive myoclonic epilepsy of Unverricht-Lundborg (EPM1), and partial epilepsy with auditory features (EPT), were also excluded as potential loci linked to the FC trait in our families. CONCLUSIONS: These findings favor considerable genetic heterogeneity for febrile convulsions.

Age of Onset↗
PubMed2000

Moderators of the effect of preoperative emotional adjustment on postoperative depression after surgery for temporal lobe epilepsy.

PURPOSE: Other outcome measures besides seizure control must be considered when assessing the benefit of epilepsy surgery. We investigated the effect of preoperative psychosocial adjustment on postoperative depression in epilepsy patients followed up prospectively for 2 years after temporal lobectomy. METHODS: The Washington Psychosocial Seizure Inventory (WPSI) evaluated psychosocial functioning; the Centre for Epidemiological Studies Depression Scale (CES-D) measured depression. Both were completed at baseline and follow-up. RESULTS: Follow-up occurred in 39 temporal lobectomy patients at 2 years after surgery. Greatest improvement in depression scores was limited to patients with good seizure outcomes (seizure free, or marked reduction in seizure frequency), and seizure outcome was a significant predictor of postoperative depression. Despite this, preoperative scores on the emotional adjustment scale of the WPSI were most highly correlated with depression 2 years after surgery. To clarify this relation, moderated hierarchic regression suggested that good preoperative emotional adjustment (WPSI) was generally associated with less depression after surgery. Moreover, poorer preoperative adjustment combined with older age, generalized seizures, the finding of preoperative neurologic deficits, a family history of psychiatric illness, and/or a family history of seizures was related to higher depression scores 2 years after surgery. CONCLUSIONS: Depression after temporal lobectomy is dependent on a complex interaction of variables and can have a significant effect on indices of postoperative adjustment. The WPSI emotional adjustment scale may help to predict which patients are likely to be chronically depressed after surgery.

Adaptation, Psychological↗
PubMed2000

Does the intracarotid amobarbital procedure predict global amnesia after temporal lobectomy?

PURPOSE: The intracarotid amobarbital procedure (IAP) is widely used to help predict who might be at risk for postoperative amnesia after unilateral temporal lobectomy for intractable seizures. We describe the memory outcome in 10 patients who underwent standard temporal lobectomy, including mesial temporal structures, despite failing the memory portion of the IAP after injections both ipsilateral and contralateral to the resected seizure focus. METHODS: Data for seven of the study subjects were obtained through a retrospective review of patients assessed on a surgical epilepsy unit during a 15-year period who failed the Montreal Neurological Institute IAP memory protocol after both ipsilateral and contralateral injections and subsequently underwent unilateral temporal lobectomy. More recently, we have studied temporal lobectomy patients who failed the Medical College of Georgia memory protocol after both ipsilateral and contralateral injections (n = 3). Preoperative and postoperative memory test scores were compared, and data regarding seizure outcome and self-perception of postoperative memory were collected. RESULTS: At follow-up, none of the patients presented with a pattern indicative of a global amnesia, and 80% demonstrated >90% improvement in their seizure disorder or were seizure-free. CONCLUSIONS: These findings indicate that bilateral memory failure on the IAP does not preclude the removal of an epileptogenic temporal lobe or a successful surgical outcome. In addition, the findings raise questions regarding the validity of the IAP and the possibility that memory may be reorganized in patients with a long history of temporal lobe epilepsy.

Adult↗
PubMed2000

Auras, seizure focus, and psychiatric disorders.

OBJECTIVE: The goal of this study was to assess the types of auras and their associations with the focus of seizures in 144 consecutive adult patients with partial epilepsy refractory to medical treatment. The association of frequency and type of aura with a psychiatric disorder was also studied. BACKGROUND: The nature of the aura, its association with the seizure focus, and its relation with emotions and behavioral dysfunction have received relatively little attention, and remain controversial. METHODS: Patients were admitted to an epilepsy investigation unit for detailed observation of their seizures and type of aura. Patients underwent standard electroencephalographic telemetry, including implanted subdural electrodes, if necessary, to delineate the seizure focus. The auras were classified into nine categories. All patients had an independent clinical psychiatric interview for a Diagnostic and Statistical Manual, Third Edition-Revised (DSM-III-R)-based diagnosis. RESULTS: Of the 144 patients studied, 111 (77.1%) had one or more symptoms during the aura and 33 (22.9%) had no aura. The most frequent aura types were viscerosensory (47 cases [32.6%]), experiential (44 cases [30.6%]), and cephalic (21 cases [14.6%]). A temporal lobe focus was present in 116 (80.5%) patients. Only experiential auras were significantly associated with a temporal lobe seizure focus (33 of 44 cases). A DSM-III-R psychiatric diagnosis was present in 74 (51.4%) patients. Of the 116 patients with a temporal lobe focus, 60 (50.2%) had a DSM-III-R psychiatric diagnosis. Patients with two or more auras were significantly more likely to have a psychiatric diagnosis (70.2%) compared with those with one aura (39.1%) or no aura (48.5%). A significant association between experiential auras and psychiatric morbidity was seen. CONCLUSIONS: Auras occurred in a majority of patients with a treatment-refractory partial epilepsy who were hospitalized for assessment of their seizure focus for possible surgical candidacy. Two or more auras were associated with a psychiatric diagnosis as was the presence of an experiential aura. Experiential auras were most common in temporal lobe epilepsy. Approximately half the patients, irrespective of seizure focus, had an associated psychiatric morbidity.

Adolescent↗
PubMed1999

EEG and clinical associations with mortality in comatose patients in a general intensive care unit.

The authors examined EEG findings and clinical factors for their association with outcome in comatose patients in their general intensive care unit. The following individual and combinations of factors were strongly related to mortality, with positive predictive values of >0.80 and odds ratios >2.0: age over 65 years, anoxic/ischemic encephalopathy, EEG suppression, lack of EEG reactivity; anoxia-ischemia with partial or complete cranial nerve areflexia, anoxia-ischemia with EEG suppression; anoxia-ischemia and generalized epileptiform activity; anoxia-ischemia with partial cranial nerve areflexia and EEG suppression. Conversely, the following factors favored survival rather than death: systemic infection/sepsis, metabolic derangement (excluding anoxic-ischemic insult), trauma; dysrhythmia, focal epileptiform activity, and regional delta and reactivity on EEGs. The findings of this study support the integration of these data into intensive care unit prognostic scoring systems, such as later versions of the Acute Physiology and Chronic Health Evaluation (APACHE).

Coma↗
PubMed1999

The effect of sevoflurane and isoflurane anesthesia on interictal spike activity among patients with refractory epilepsy.

UNLABELLED: The electrophysiologic effects of sevoflurane are not well characterized in humans. Among patients with refractory epilepsy, this study compared 1) electroencephalographic (EEG) interictal spike activity during wakefulness and sevoflurane anesthesia, and 2) electrocorticographically (ECoG) recorded interictal spike activity during sevoflurane and isoflurane anesthesia. We studied 12 patients undergoing insertion of subdural electrodes. Before commencing anesthesia, awake (baseline) EEG recordings were obtained. After inhaled induction, EEG interictal spike activity was evaluated during stable, normocapnic, and hypocapnic (Paco2 = 28-30 mm Hg), sevoflurane anesthesia administered at 1.5 times the minimum alveolar anesthetic concentration (1.5 MAC). Immediately after surgery, ECoG recordings were obtained from subdural electrodes during 1) 1.5 MAC isoflurane, 2) 0.3 MAC isoflurane, and 3) 1.5 MAC sevoflurane anesthesia. EEG spike frequency increased in all patients during sevoflurane anesthesia compared with awake recordings (P = 0.002). Compared with 0.3 MAC isoflurane anesthesia, ECoG interictal spike frequency was higher in all patients during 1.5 MAC sevoflurane anesthesia (P = 0.004) and in 8 of 10 patients during 1.5 MAC isoflurane anesthesia (P = 0.016). Under sufficiently rigorous conditions, both sevoflurane and isoflurane can provoke interictal spike activity at near burst-suppression doses. This property is more prominent with sevoflurane than isoflurane. IMPLICATIONS: The results of this study suggest that the capacity to modulate neuroexcitability is a dose-dependent feature of volatile anesthetics that is manifested most prominently at near burst-suppression doses (i.e., 1.5 times the minimum alveolar anesthetic concentration) and is minimal or absent at low doses.

Adolescent↗
PubMed1998

The Canadian Epilepsy Database and Registry.

Epilepsy encompasses medical, psychological, social and demographic factors which are best studied in large populations. The Canadian Epilepsy Database and Registry (CEDAR) is a comprehensive English language, multicentre epilepsy database which has been developed to study the impact of these and other factors on epilepsy in Canada. In addition, it can be used locally in the clinic for office record keeping, automated printout of a referral letter or graphing seizures and other data over time. The data in CEDAR are similar to what is found in the patient's chart. There are 20 participating centres across Canada which have entered data on over 8000 adult and pediatric epilepsy patients. The information in CEDAR will be available for research purposes to centres entering data as well as to academic researchers, the pharmaceutical industry and government agencies.

Canada↗
PubMed1998

Antiepileptic drug treatment following temporal lobectomy.

Antiepileptic drug use was documented before and after temporal lobectomy. Carbamazepine, phenytoin, and clobazam were the most commonly used drugs, both pre- and postoperatively. Preoperatively, polytherapy was used in 78% of patients; at 6 months follow-up, 47%; at 12 months, 18%; and at 24 months, 14%. Preoperatively, monotherapy was used in 20% of patients; at 6 months follow-up, 49%; at 12 months, 55%; and at 24 months, 42%. No medication was used preoperatively by 2% of patients; at 6 months follow-up, 2%; at 12 months, 27%; and at 24 months, 44% (p < 0.001). After 2 years, 53% of patients who were seizure free had stopped taking medication, as had 33% who had some seizures after surgery.

Adolescent↗
PubMed1998

MR in temporal lobe epilepsy: analysis with pathologic confirmation.

PURPOSE: We evaluated the MR findings in patients with temporal lobe epilepsy to determine the predictive value of MR imaging in assessing patient outcome. METHODS: MR studies from 186 of 274 consecutive patients who underwent temporal lobectomy for intractable epilepsy were reviewed retrospectively. Images were interpreted by an experienced neuroradiologist, who was blinded to the side of seizure activity and to pathologic findings. RESULTS: MR imaging exhibited 93% sensitivity and 83% specificity in detecting hippocampal/amygdalar abnormalities (n = 121), and 97% sensitivity and 97% specificity in detecting abnormalities in the rest of the temporal lobe (n = 60). Abnormal high signal of the hippocampus on T2-weighted images had a sensitivity of 93% and specificity of 74% in predicting mesial temporal sclerosis (n = 115). The presence of hippocampal atrophy on MR correlated with the duration of seizures. Sensitivity and specificity of MR imaging in detecting temporal lobe tumors (n = 42) were 83% and 97%, respectively, based on abnormal signal and mass effect. After surgery, 63% of patients were seizure free and 28% had a significant reduction of seizure frequency at an average of 24 months (range, 12 to 78 months) after surgery. Patients with a single lesion in the anterior temporal lobe or hippocampus/amygdala had a better outcome than patients with multiple lesions (n = 22). Interrater agreement varied from 0.4 to 0.93, with best agreement for tumors or abnormal hippocampal signal on T2-weighted images. CONCLUSION: MR imaging is highly sensitive in detecting and locating abnormalities in the temporal lobe and the hippocampus/amygdala in patients with temporal lobe epilepsy. Hippocampal atrophy appears to correspond to the duration of seizure disorder.

Adult↗
PubMed1997

Health-related quality of life and seizure control in temporal lobe epilepsy.

We conducted a prospective study over 24 months to compare health-related quality of life in surgically and medically treated patients with intractable temporal lobe epilepsy. Seizure frequency and health-related quality of life were assessed in 81 patients before and 6, 12, and 24 months after treatment. Using the Epilepsy Surgery Inventory 55 (ESI-55), we compared (1) different seizure outcome groups and (2) temporal lobectomy with continuing medical management. Follow-up was satisfactory in 72 patients (89%), 51 treated with temporal lobectomy and 21 with no surgery. Pretreatment seizures and health-related quality of life were comparable in the two groups. Seizure outcome was significantly better at 6, 12, and 24 months after surgery. At 24 months, seizure-free patients and those with at least a 90% reduction in seizure frequency reported significant improvements in health-related quality of life (on 5 of 10 subscales and overall Epilepsy Surgery Inventory 55 scale). Deterioration in quality of life occurred with less than 90% seizure reduction. Only one Epilepsy Surgery Inventory 55 subscale at 6 months and two subscales at 12 months showed a significant difference. Patients with good seizure outcome experience improved health-related quality of life after treatment. Since temporal lobectomy results in considerably better seizure control than continued medical management, the findings support surgery as the preferred treatment, although changes in health-related quality of life may not be evident until the second postoperative year.

Adolescent↗